Allocation of station addresses to communication users in a bus system

ABSTRACT

The invention relates to a method for simplified allocation of station addresses to communication users in a bus system, and communication users in a bus system. A first communication user, which can automatically transmit to the bus, can allocate data to a station address, said data clearly identifying another communication user, or characterizing a station address as non-occupied. An additional communication user who has already sent a data packet with clearly identifying data to the first communication user in an earlier communication cycle by means of said communication user and who receives a data packet comprising data in a later communication cycle, whereby said data does not clearly identify said communication user, can automatically alter the station address thereof in a station address characterized as not being occupied.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to the German application No.10330596.3, filed Jul. 7, 2003 and to the International Application No.PCT/EP2004/007120, filed Jun. 30, 2004 which are incorporated byreference herein in their entirety.

FIELD OF INVENTION

The invention relates to a method for allocation of station addresses tocommunication users in a bus system, and communication users in a bussystem.

BACKGROUND OF INVENTION

The bus system has generally come to predominate in digital technologyfor the transfer of information between individual users in a system, inother words communication between users. A bus system is characterizedin that several communication users are connected on the input sideand/or output side in parallel to a shared bus. A bus system is thus adevice for collective communication between several users, each userbeing able to associate with every other user directly. A distinction ismade between parallel and serial bus systems. Data is mostly exchangedon a bit-parallel and byte-serial basis, but bit-serial operation isalso possible. Depending on the variant, these are known as parallel orserial bus systems. Bit-parallel buses are preferably used fortransmitting high data rates over short distances, e.g. within acomputer. The merits of bit-serial buses lie in the small outlay fordrivers, connectors and transmission lines (often simple two-wirelines). Data transmission is unproblematic even over large distances andthe hardware requirement for any electrical isolation needed iscomparatively small.

SUMMARY OF INVENTION

Communication users in a bus system, e.g. communication users linked toa serial bus, normally require a unique station address to be able tocommunicate with one another. In the past various methods have been usedwith serial bus systems to assign station addresses for the individualcommunication users. Normally this involves a manual setting via codingswitches at the communication users or assigning an address in advancevia the bus, whereby it must be possible to address every communicationuser from the outset. In other customary methods the station address isarrived at on the basis of the position of the communication user on thebus. The data traffic in such a system is generated by what is known asa bus master, to which the structure of the bus must be known. Addressconflicts cannot occur in such a case. The bus master generates aprecisely specified data frame which has as many data fields as thenumber of data users connected on the bus. This data frame is sent fromone communication user to the next, each user being able to extract itsdata and to send new data for the bus master. This method isparticularly problematic if a communication user has to be exchanged andthe bus master does not recognize this change immediately. As a resultthe data frame is displaced and specific data no longer reaches theright recipient. The methods described for assigning addresses areeither very prone to error, like manual assignment with coding switches,or already require a uniqueness attribute for the individualcommunication users before the address can be assigned. This uniquenessattribute must be known to both the address assignment unit and thecommunication users.

An object of the invention is to simplify the allocation of stationaddresses to communication users in a bus system.

This object is achieved by a method for allocating station addresses tocommunication users in a bus system, whereby exactly one firstcommunication user able to transmit automatically on a bus can allocateto a station address data that uniquely identifies another communicationuser, or a station address can be characterized as non-occupied, inwhich method in each communication cycle

the first communication user in each case sends a first data packet toeach station address, whereby the first data packet if necessarycontains data allocated to the respective station address, said datauniquely identifying another communication user,

one or more other communication users each send the first communicationuser a second data packet containing their station address and datauniquely identifying the respective other communication user, wherebythe data uniquely identifying the respective other communication user isallocated to the respective station address by the first communicationuser and

the first communication user sends all other communication users a thirddata packet containing the information about which station addresses arecharacterized as non-occupied,

whereby a communication user that in an earlier communication cyclealready sent the first communication user a second data packetcontaining data uniquely identifying this communication user and that ina subsequent communication cycle receives a first data packet containingdata not uniquely identifying this communication user automaticallyalters the station address thereof to one of the station addressescharacterized as non-occupied.

This object is achieved by a communication user in a bus system whichcan automatically transmit on a bus and has means for allocating to astation address data uniquely identifying another communication user andmeans for characterizing a station address as non-occupied.

This object is achieved by a communication user in a bus system whichhas means for sending a first communication user second data packetscontaining data uniquely identifying the communication user and whichcan automatically alter the station address thereof.

The invention is based on the idea of having communication usersthemselves undertake the assignment of station addresses tocommunication users in a bus system, in particular in a serial bussystem, using centrally available information. The inventive methodensures that the station addresses of the communication users areunique. Multiply assigned station addresses are automatically identifiedand address conflicts that occur are resolved locally by the affectedcommunication users automatically by randomly selecting a potentiallyfree, non-occupied station address. This thus involves a method forautoconfiguration of station addresses. Already assigned stationaddresses of addressable communication users are not affected by this.Thus all communication users can be reached and addressed. The methoddoes not involve a central assignment of station addresses, but it canform the prerequisite for this. In the inventive method all validphysical station addresses in the bus system can be used completelyfreely. There is no need for relationships, for example with thephysical position of the communication user, nor is the address space inany way restricted. The method does not require additional wiringbetween the communication users or particular restrictions as regardsthe topology. It can be applied to the bus topology finally set up foran operation. Since the station address is administered by thecommunication user itself, disruptions or addressing errors are ruledout even when a communication user is exchanged, e.g. when a module isexchanged.

Mixed configurations with communication users having no means fortransmitting to a first communication user second data packetscontaining data uniquely identifying the respective communication userand not being able to automatically change their station address arepossible without negatively affecting these communication users.

The communication cycle is repeated with a particular cycle duration. Inorder to burden communication resources as little as possible withsending, forwarding, receiving and processing the data packets requiredfor the allocation of station addresses to communication users, it isproposed in accordance with an advantageous embodiment of the inventionthat the cycle duration of the communication cycle is variable. Thus thecycle duration can, for example in an initial phase in which theaddressing has not as yet progressed very far, be selected to be smallerin comparison to a later phase in the addressing procedure in whichthere is less need for addressing. In particular, following a successfulconclusion of the allocation of station addresses to communication usersthe described communication cycle can be performed only with acomparatively large cycle duration in comparison to other communicationcycles, in order for example to be able to respond to changes in the bussystem as a result of the exchange or failure of communication users andthe like.

On the basis of the inventive method for allocating station addresses tocommunication users in a bus system an advantageous embodiment of themethod is proposed, in which device information can be stored in storagemeans of the other communication users, it being possible for thestorage means to be addressed via the bus by the first communicationuser and for the device information to be read out by the firstcommunication user. Thus for example all device information needed foran automatic configuration can be stored directly in a memory of theother communication users. For reading out, a message-orientedtransmission method, as already defined for most serial bus systems, isfor example used. Thus an up-to-date picture of the device informationof every other communication user located on the bus is available to thefirst communication user at all times. The device information comprises,for example, an identification and possible configurations andparameterizations.

Thus project planning and maintenance for a bus system is possiblewithout device information supplied by the manufacturer in the form ofelectronic data sheets. Thus it is possible to automate further steps inthe project planning of a bus system, in particular of a serial bussystem. When using this advantageous embodiment of the invention acomparison between the projected communication users with theirconfiguration and parameterization and the situation actually prevailingon the bus is always available to a project planner. Thus projectplanning errors, errors in wiring and the choice of communication userscan be analyzed at a central point and correspondingly rectified.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described and explained in more detail below on thebasis of the exemplary embodiments shown in the figures.

The figures show:

FIG. 1 a bus system with communication users,

FIG. 2 a first data packet,

FIG. 3 a third data packet,

FIG. 4 the communication between a first communication user and othercommunication users,

FIG. 5 the communication between a first communication user and anothercommunication user without an address conflict,

FIG. 6 the communication between a first communication user and anothercommunication user without means for sending second data packets and

FIG. 7 the communication between a first communication user and othercommunication users when an address conflict is present.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a serial bus system 9 with communication users 1, 2. Thecommunication users 1, 2 are interconnected via a bus 3. A firstcommunication user 1 in the bus system 9 has means 7 for allocating to astation address 6 data uniquely identifying another communication user 2and for characterizing a station address 6 as non-occupied. The firstcommunication user 1 can in each case send a first data packet 4 to eachstation address 6, the first data packet 4 if necessary containing dataassigned to the respective station address 6 and uniquely identifyinganother communication user 2. The other communication users 2 in the bussystem 9 have means 8 for sending the first communication user 1 seconddata packets 5 containing data uniquely identifying the respectivecommunication user 2 and can automatically and independently changetheir station address 6.

FIG. 2 shows a first data packet 10. The first data packet 10 has afirst section 11 containing the name of the data packet. Furtherinformation on the structure of the first data packet is contained in asecond section 12 of the first data packet 10, for example anidentification of the data packet and data that uniquely identifiesanother communication user, such as for example component data and/or aserial number.

FIG. 3 shows a third data packet 13. The third data packet 13 has afirst section 14 containing the name of the third data packet. Furtherinformation on the structure of the third data packet 13 is contained ina second section 15 of the third data pack et 13. Examples of suchinformation include an identification of the third data packet, statusinformation, information on critical bus parameters and/or informationabout which station addresses are characterized as non-occupied.

FIG. 4 shows the communication between a first communication user, knownas the ACFG manager 20, and other communication users, in this case fourso-called ACFG agents 22 to 25 (ACFG=autoconfiguration) and anothercommunication user 26. The communication users are therefore eachallocated one of two different roles. The ACFG manager 20 assumes thecontrolling role for the so-called ACFG mechanism. Only one ACFG manager20 may be active on the bus system at a time. An ACFG manager 20 must beable to transmit automatically on the bus. In bus systems based on themaster-slave principle, the ACFG manager 20 must always be a master.Other communication users connected on the bus system can each assumethe role of an ACFG agent 22-25.

The ACFG manager 20 has, as means for allocating to a station addressdata uniquely identifying another communication user and forcharacterizing a station address as non-occupied a database in a memory,known as the system MIB (MIB=Management Information Base). In the systemMIB 21 each possible station address in the bus system is allocatedeither a communication user or the information that this station addressis not occupied. The ACFG manager 20 can autonomously send data packetson the bus. FIG. 4 shows various data packets. In general data packetsare also called PDUs (Protocol Data Units). PDUs sent by the ACFGmanager 20 are called request PDUs. PDUs sent by communication users inreply to the request PDUs are called response PDUs.

The ACFG manager 20 initiates a communication cycle, also called an ACFGcycle, in which all station addresses possible in the correspondingserial bus system are addressed. In the exemplary embodiment in FIG. 4 acommunication cycle for allocating station addresses to communicationusers is shown by way of example. The chronological sequence of the datapackets corresponds in principle to the direction of the time arrow t.At the start of the communication cycle the ACFG manager 20 sends whatis known as an SDD request PDU 34 (SDD =Systems Data Distribution) bybroadcast 27 to all users in the bus system. The SDD request PDU 34 isan exemplary embodiment of a third data packet 13 in accordance withFIG. 3. By means of the SDD request PDU 34 all station addressescharacterized as non-occupied are announced by the ACFG manager 20 inthe bus system. Each ACFG agent saves in each ACFG cycle the list offree bus addresses contained in the SDD request PDU 34.

The request PDUs illustrated below are what are known as NAN requestPDUs 35-40 (NAN New Agent Notification). A NAN request PDU is anexemplary embodiment of a first data packet 10 in accordance with FIG.2. The NAN request PDU 35-40 contains where necessary informationuniquely identifying a communication user. The ACFG manager 20 sends aNAN request PDU 35-40 to every available station address 28-33. If thestation addresses 28, 30 are not occupied by a communication user, theACFG manager 20 does not receive a corresponding response PDU to therespective NAN request PDU 35 or 27. In this case the ACFG manager 20characterizes these station addresses in its system MIB as non-occupied.All station addresses to which no reply is given contain, for example,the entry “free” in the system MIB 21. All station addresses with thisentry are simultaneously published as a broadcast message at the startof each ACFG cycle by means of an SDD request PDU 34 to allcommunication users.

If a NAN request PDU 36, 40 is sent to a station address 29 or 33 whichis allocated to an ACFG agent 22 or 25 participating in the describedprocedure, the ACFG manager 20 in each case receives a NAN response PDU41 or 42 having data uniquely identifying the respective ACFG agent 22or 25. A station address 29, 33 to which a response is given with such acorrect NAN response PDU 41, 41 contains the entry “ACFG agent” in thesystem MIB 21 of the ACFG manager 20. Additionally the transmitted dataof the respective NAN response PDU 41, 42 is recorded. The communicationuser with this station address is then addressed with a NAN request PDU36, 40, the contents of which correspond to the NAN response PDU 41, 42.The communication user thus continually has the assurance that it iscorrectly identified by the ACFG manager 20 as exactly this ACFG agentand has been included in the system MIB 21.

If a station address is allocated simultaneously to several ACFG agents23, 24, an address conflict arises and the ACFG manager 20 likewisereceives no valid NAN response PDU and this station address 31 would becharacterized in its system MIB 21 as non-occupied.

If a NAN request PDU 39 is sent to a station address 32 used by acommunication user 26 not using the described method, this communicationuser 26 will send a PDU 43 to the ACFG manager 20, which howevercontains none of this data uniquely identifying this communication user26. The communication user 26 is identified by the ACFG manager 20 as acommunication user without ACFG agent functionality. In this case theACFG manager 20 will allocate the attribute “not an ACFG agent” to thecorresponding station address 32. The station address 32 continues to beaddressed with a NAN request PDU—in this case the same one as during theprevious addressing.

FIG. 5 shows the communication between a first communication user andanother communication user without an address conflict. The firstcommunication user, in accordance with FIG. 4 the ACFG manager 20 with asystem MIB 21, sends data packets to the ACFG agent 22 via a bus notshown here. FIG. 5 shows two communication cycles for allocating stationaddresses, the start of a communication cycle in each case beingindicated by a broken line. The time progression is again symbolized bya time arrow t. In the first communication cycle a NAN request PDU 36 issent to the station address 29 allocated to the ACFG agent 22 after themandatory SDD request PDU 34. The ACFG agent 22 then sends a NANresponse PDU 41 in reply, containing information uniquely identifyingthis ACFG agent 22. The ACFG manager 20 then in its system MIB allocatesto the station address 29 this information characterizing the ACFG agent22. In a second following communication cycle the ACFG manager 20 sendsthe station address 29 a NAN request PDU 50 containing the informationuniquely identifying the ACFG agent 22. The ACFG agent 22 thenrecognizes that the ACFG manager 20 has allocated it to the correctstation address and in reply again sends the NAN response PDU 41.Corresponding to the second communication cycle further followingcommunication cycles are executed in respect of this station address andthis ACFG agent 22.

FIG. 6 shows the communication between a first communication user andanother communication user having no means for sending second datapackets. The first communication user, in accordance with FIGS. 4 and 5the ACFG manager 20 with a system MIB 21, sends an SDD request PDU 34 ina first communication cycle to all communication users by means of abroadcast 27. The ACFG manager 20 sends a NAN request PDU 39 to thestation address 32. The communication user 26 to whom this stationaddress 32 is allocated has however no means for sending second datapackets having data uniquely identifying the communication user andhence sends in reply a PDU 43 not containing any data uniquelyidentifying this communication user 26 or the communication user 26sends no reply or no data packet at all. The ACFG manager 20 thenallocates the information or attribute “not an ACFG agent” in its systemMB to the respective station address 32. In all other furthercommunication cycles the ACFG manager 20 again sends a NAN request PDU39 to the station address 32 and in reply receives from thecommunication user 26 in each case a PDU 43 not containing dataidentifying this communication user.

FIG. 7 shows the communication between a first communication user andother communication users when an address conflict occurs. Again severalcommunication cycles are illustrated, following one another in thedirection of the time arrow t, the start of which is indicated in eachcase by a broken line. The first communication user in the exemplaryembodiment according to FIG. 7 is again the ACFG manager 20 having asystem MB 21 for allocating information to station addresses. At thestart of each communication cycle shown here the ACFG manager 20 sendsan SDD request PDU 34 by broadcast 27 to all station addresses or allcommunication users containing the information about non-occupiedstation addresses. In the first communication cycle shown here the ACFGmanager 20 sends a NAN request PDU 38 to the station address 31.However, this station address 31 is simultaneously allocated to twodifferent ACFG agents 23 and 24. The ACFG manager 20 then receives noresponse PDU uniquely identifying an individual ACFG agent and hencecharacterizes the station address 31 as non-occupied in its system MIB21.

In a second communication cycle this station address 31 characterized asnon-occupied is therefore again sent a NAN request PDU 38 by the ACFGmanager 20 which does not contain information uniquely identifying oneof the two ACFG agents 23 or 24. Both ACFG agents 23 and 24 therebyrecognize that they could not be uniquely allocated to the stationaddress 31 by the ACFG manager 20 and then automatically select forthemselves a new station address 51 or 52 from the pool of stationaddresses characterized as non-occupied which were notified by broadcast27 by means of the SDD request PDU 34. Thus an address conflict issignaled in the ACFG agent 23, 24 if the ACFG agent 23, 24 does notreceive the contents of its own NAN response PDU after receipt of a NANrequest PDU 38 in the next ACFG cycle. In this case the ACFG agent 23,24 withdraws from the bus and returns to the bus with a randomlyselected station address from its list of free station addresses. Thisprocedure is repeated until the station address of the ACFG agent 23, 24is recognized by the ACFG manager 20 and has been included in the systemMIB 21 thereof.

In the third communication cycle shown here the ACFG manager 20 willsend these station addresses 51 and 52 previously characterized asnon-occupied a NAN request PDU 38 not containing information uniquelyidentifying a communication user. The ACFG agents 23 and 24 reply tothis NAN request PDU 38 in each case with a NAN response PDU 53 or 54containing information uniquely identifying the respective ACFG agents23 and 24. The ACFG manager 20 can then allocate the station addresses51 and 52 the corresponding information contained in the NAN responsePDUs 53 or 54. In the following communication cycle the ACFG manager 20then sends the respective station address 51 or 52 NAN request PDUs 55and 56 containing the information uniquely identifying the respectiveACFG agents 24 or 23. The ACFG agents 23 and 24 reply with thecorresponding NAN response PDUs 54 or 53.

All station addresses on which there is an address conflict can havevery different reactions depending on the bus system, topology andconfiguration of the respective bus system. Within the describedprocedure for autoconfiguration the reactions described below areexpected and overcome. In a first case the ACFG manager 20 does notreceive an answer from this station address because the data packet hasbeen so destroyed by overlaying that no interpretation is possible. Inthis case this station address is again addressed in the next ACFG cyclewith a NAN request PDU without corresponding data contents of the ACFGagent. The ACFG agent recognizes that the communication to the ACFGmanager 20 was not successful and automatically alters the stationaddress thereof. In a second case the ACFG manager 20 receives anunknown reply from this station address because the data packet has beencorrupted by overlaying but not completely destroyed. In this case thisstation address is addressed again in the next ACFG cycle with a NANrequest without corresponding data contents of the ACFG agent. The ACFGagent also recognizes in this case that the communication to the ACFGmanager 20 was not successful and automatically alters the stationaddress thereof. In a third case the ACFG manager 20 receives a correctNAN response PDU from this station address, because one of the telegramsof the different ACFG agents was able to prevail electrically on thetransmission medium. This behavior can be observed in the case ofparticular topologies with very long bus lines, repeaters or couplersfor linking different physical media if an ACFG agent is located veryclose to the ACFG manager 20 and another ACFG agent is relatively faraway or is located in another bus segment. Very different response timesemerge from this for the two ACFG agents. In this case the ACFG manager20 sends a NAN request PDU in the next cycle with the data contents ofone of the ACFG agents. All other ACFG agents located on this stationaddress recognize that the communication to the ACFG manager 20 wasunsuccessful and alter the station address thereof.

According to another exemplary embodiment all device information neededfor an automatic configuration is stored directly in the memory of theACFG agent. This memory can be uniquely addressed via the bus from theACFG manager 20 so that the ACFG manager 20 can automatically read outall device information needed for the configuration from the ACFGagents. A message-oriented transmission method is used, for example, forreading out, as already defined for most serial bus systems. Thus anup-to-date picture of the device information of every ACFG agent locatedon the serial bus is available in the system MIB 21 of the ACFG manager20 at all times. The device information essentially consists of anidentification and possible configurations and parameterizations. On thebasis of this data, project planning of the serial bus is possiblewithout extra device information supplied by the manufacturer in theform of electronic data sheets.

According to another embodiment it is possible to predefine expectedproject planning data in the ACFG manager 20. In this case the expectedproject planning data is compared to the actual current status on theserial bus and any divergences are displayed. This is visualized withthe aid of corresponding displays on all ACFG agents, so that projectplanning progress and error events can be recognized in every part of asystem. Thus a project planner always has available a comparison betweenthe projected communication users with their configuration andparameterization and the situation actually prevailing on the serialbus. Thus project planning errors, errors when setting up the bussystem, errors in wiring and the choice of communication users can beanalyzed and correspondingly rectified significantly more easily at onecentral point.

When specifying expected project planning data it is possible but notnecessary to assign desired station addresses for all communicationusers located on the bus. If station addresses have been projected, theycan be assigned very easily by the ACFG manager 20 on the basis of thebehavior when resolving address conflicts. Within a few iteration stepsacross all station addresses all projected station addresses can beassigned one after the other. Address conflicts which then arise againare resolved by the ACFG agents automatically. Only those ACFG agents towhich no projected station address has as yet been allocated temporarilyaccept a random free station address. All other ACFG agents retain theirexplicitly allocated station address.

Another embodiment of the method relates to the unique identification ofcommunication users where this is not possible on the basis of theproject planning data. In this case an acyclic communication channel isopened between the ACFG manager 20 and the ACFG agents which cannot beallocated to the project planning. Manual identification takes place bymeans of a sequence of read and write commands and correspondingdisplays and input aids for the ACFG agents.

In summary, the invention thus relates to a method for simplifiedallocation of station addresses 6 to communication users 2 in a bussystem 9, and communication users 1, 2 in a bus system 9. Exactly onefirst communication user 1 able to transmit automatically on the bus 3can then allocate data to a station address 6, said data uniquelyidentifying another communication user 2 or characterizing a stationaddress 6 as non-occupied. Another communication user 2 that in anearlier communication cycle already sent the first communication user 1a data packet containing data uniquely identifying this communicationuser 2 and that in a subsequent communication cycle receives a datapacket 10 containing data not uniquely identifying this communicationuser 2 can automatically alter the station address 6 thereof into astation address 6 characterized as non-occupied.

1. A method of allocating station addresses to communication usersarranged in a bus system, wherein communication on the bus system isorganized in communication cycles, and a first communication user on thebus assigned a controlling role as a manager and having a databasecomprising a list of each possible station of the bus and a currentallocation for each station address as either a communication user or anon-occupied station address is configured to: autonomously transmitdata to all station addresses on the bus system, allocate data to a eachstation address in the database, the data uniquely identifying acommunication user, or characterize the station address as notallocated, the method comprising: transmitting in a first communicationcycle, by a first communication user on the bus, to all stationaddresses on the bus: (a) a first broadcast request comprising a list ofcurrently non-occupied station addresses from the database of the firstcommunication user so that all other users on the bus can save the listof currently non-occupied station addresses; and (b) a first new agentrequest to all station addresses on the bus requesting a new agentresponse, wherein: (i) for each non-responsive station address in whichno response is received, the current allocation is updated tonon-occupied in the database, and (ii) for each responsive stationaddress in which a response comprising data uniquely identifying theagent at that station address is received, the current allocation isupdated to a communication user and the data uniquely identifying theagent at that address is recorded in the database; transmitting in asecond communication cycle, by the manager: (a) a second broadcastrequest to all station addresses on the bus comprising the list ofcurrently non-occupied station addresses from the database of the firstcommunication user as updated in the first communication cycle so thatall other users on the bus can save the list of currently non-occupiedstation addresses; and (b) a second new agent request addressed to eachresponsive station address on the bus comprising (i) the data uniquelyidentifying the agent at that station address as recorded in thedatabase as confirmation, thereby assuring the communication user atthat station address of correct identification by the manager, and (ii)the data uniquely identifying the agent at each responsive stationaddress as recorded in the database, thereby allowing communicationsamong communication users by correct identification.
 2. The methodaccording to claim 1, wherein the communication cycles have a variablecycle time.
 3. The method according to claim 1, further comprising:storing device information comprising data uniquely identifying theagent in a memory device assigned to the communication user; accessingthe stored device information via the bus system by the firstcommunication user; and reading the stored device information by thefirst communication user.
 4. The method according to claim 3, furthercomprising automatically configuring the bus system by repeating themethod steps.
 5. A communication user in a bus system adapted to performthe steps of claim
 1. 6. The method of allocating station addresses ofclaim 1 further comprising the first new agent request of the firstcommunication cycle (iii) for each non-agent responsive station addressin which the response is received but does not comprise data uniquelyidentifying the agent at that station address, the current allocation inthe database for that station address is updated to a communication userwithout agent functionality, providing for communications with thecommunication user at that non-agent responsive station address withoutunique identification.
 7. The method of allocating station addresses ofclaim 6 further comprising in the first new agent request of the firstcommunication cycle (iv) for each conflicting station address, havingmore than one agent allocated thereto, no response is received, and thecurrent allocation is updated to non-occupied in the database, so thatthe transmission by the manager during the second cycle identifying theconflicting station address as non-occupied signals the more than oneagent allocated to the conflicting station address of the conflict sothat the more than one agent allocated to the conflicting stationaddress can automatically select a new station address from the list ofcurrently non-occupied station addresses.
 8. The method of allocatingstation addresses of claim 1 wherein the second new agent requestcomprises a data packet wherein a section of the data packet includesthe data uniquely identifying the agent at each responsive stationaddress.
 9. The method of claim 8 wherein the data uniquely identifyingthe agent comprises component data or a serial number or both.
 10. Themethod of allocating station addresses of claim 1 wherein the broadcastrequest comprises a data packet wherein a section of the data packetincludes list of currently non-occupied station addresses.
 11. A methodof allocating station addresses to communication users arranged in a bussystem that requires unique stations addresses for communication usersto be able to communicate with one another, wherein communication on thebus system is organized in communication cycles, comprising:transmitting in a first communication cycle, by a first communicationuser on the bus assigned a controlling role as a manager and having adatabase comprising a list of each possible station of the bus and acurrent allocation for each station address as either a communicationuser or a non-occupied station address, to all station addresses on thebus: (a) a first broadcast request comprising a list of currentlynon-occupied station addresses from the database of the firstcommunication user so that all other users on the bus can save the listof currently non-occupied station addresses; and (b) a first new agentrequest to all station addresses on the bus requesting a new agentresponse, wherein: (i) for each non-responsive station address in whichno response is received, the current allocation is updated tonon-occupied in the database, and (ii) for each responsive stationaddress in which a response comprising data uniquely identifying theagent at that station address is received, the current allocation isupdated to a communication user and the data uniquely identifying theagent at that address is recorded in the database; transmitting in asecond communication cycle, by the manager: (a) a second broadcastrequest to all station addresses on the bus comprising the list ofcurrently non-occupied station addresses from the database of the firstcommunication user as updated in the first communication cycle so thatall other users on the bus can save the list of currently non-occupiedstation addresses; and (b) a second new agent request addressed to eachresponsive station address on the bus comprising (i) the data uniquelyidentifying the agent at that station address as recorded in thedatabase as confirmation, thereby assuring the communication user atthat station address of correct identification by the manager, and (ii)the data uniquely identifying the agent at each responsive stationaddress as recorded in the database, thereby allowing communicationsamong communication users by correct identification.
 12. The method ofallocating station addresses to communication users of claim 11 furthercomprising in the first new agent request of the first communicationcycle (iii) for each non-agent responsive station address in which theresponse is received but does not comprise data uniquely identifying theagent at that station address, the current allocation in the databasefor that station address is updated to a communication user withoutagent functionality, providing for communications with the communicationuser at that non-agent responsive station address without uniqueidentification.
 13. The method of allocating station addresses tocommunication users of claim 12 further comprising in the first newagent request of the first communication cycle (iv) for each conflictingstation address, having more than one agent allocated thereto, noresponse is received, and the current allocation is updated tonon-occupied in the database, so that the transmission by the managerduring the second cycle identifying the conflicting station address asnon-occupied signals the more than one agent allocated to theconflicting station address of the conflict so that the more than oneagent allocated to the conflicting station address can automaticallyselect a new station address from the list of currently non-occupiedstation addresses.
 14. The method of allocating station addresses ofclaim 11 wherein the second new agent request comprises a data packetwherein a section of the data packet includes the data uniquelyidentifying the agent at each responsive station address.
 15. The methodof claim 14 wherein the data uniquely identifying the agent comprisescomponent data or a serial number or both.
 16. The method of allocatingstation addresses of claim 11 wherein the broadcast request comprises adata packet wherein a section of the data packet includes list ofcurrently non-occupied station addresses.
 17. A communication user in abus system adapted to perform the steps of claim 11.